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Abstract:

In a method and an apparatus for replacing old underground conduits (4),
the old conduit (4) is first laid bare with the aid of a ground drilling
device (8) with an overdrilling head and then, in turn, a new conduit (5)
is drawn in with the aid of the drill rods (7) and at the same time--in a
uniform operating step--the old conduit is pulled out of the ground.

Claims:

1. Apparatus for replacing a buried old conduit with a new conduit,
comprising: a mounting; a rod assembly coupled to the new conduit; and a
pulling drive movably supported on the mounting and operatively connected
to the rod assembly and to the old conduit.

2. The apparatus of claim 1, further comprising two clamps in spaced
apart relationship on the mounting for releasably clamping the old
conduit.

3. The apparatus of claim 1, wherein the rod assembly is comprised of
single interconnected rod members.

4. The apparatus of claim 1, further comprising a clamp arranged in a
pulling direction behind the pulling drive, and a cutting blade placed
adjacent the clamp at a side distal to the drive to separate a part of
the old conduit as the old conduit is pulled out.

5. The apparatus of claim 1, wherein the pulling drive is operatively
connected to the rod assembly and supported on the mounting for movement
between a forward position in which the pulling drive is clamped to the
old conduit for simultaneously pulling out the old conduit and drawing in
the new conduit in a same direction, and a rearward position in which the
pulling drive is decoupled from the old conduit.

6. The apparatus of claim 5, wherein the pulling out of the old conduit
and the drawing in of the new conduit are realized simultaneously in
increments as the pulling drive shuttles between the forward and rearward
positions.

7. The apparatus of claim 1, wherein the mounting extends at an incline.

Description:

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application is a divisional of prior filed copending U.S.
application Ser. No. 12/441,066, filed Mar. 12, 2009, the priority of
which is hereby claimed under 35 U.S.C. §120, and which is the U.S.
National Stage of International Application No. PCT/EP2007/007828, filed
Sep. 7, 2007, which designated the United States and has been published
as International Publication No. WO 2008/031536 and which claims the
priority of German Patent Application, Serial No. 10 2006 043 772.1,
filed Sep. 13, 2006, pursuant to 35 U.S.C. 119(a)-(d).

[0002] The content of U.S. application Ser. No. 12/441,066 is incorporated
herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0003] The invention relates to a method of replacing old underground
conduits, which involves initially laying bare the old conduit, without
altering its course in the ground, and then removal thereof from the
ground and drawing in a new conduit, and which claims the priority of
German patent application 10 2006 043 772.1, the content of which is
incorporated by reference.

[0004] Methods of this type are known; German Patent document 195 04 484
C1 describes a device for removing buried cables with the aid of a
ring-shaped drill head moving over the cable and equipped with nozzles
for a flushing liquid. Soil surrounding the cable or several cables is
washed away with the assistance of the nozzles to thereby expose the
cable which then can be pulled out from the ground. The device has an
eccentric connection for a hollow rod assembly comprised of individual
rod sections connected to one another. The hollow rod assembly meets two
tasks; Firstly, it supplies the device with flushing liquid, and
secondly, it propels the device between a starting pit on one hand and a
destination pit on the other hand.

[0005] When the device has washed the conduit free and reached the
destination pit, the exposed cable is pulled out of the created borehole
and, after removal of the flushing device, a connection adapter is
secured to the rod assembly for attachment of one or more conduits. These
conduits are then pulled into the flushing borehole with the aid of the
rod assembly in the direction of the starting pit.

[0006] A further multistage method for trenchless replacement of
underground conduits is described in the German patent document 102 11
833 (GB patent document 2 386 767). This device is additionally equipped
with a boring bit and a further tool on its rearward end. It lays bare
the buried conduit in the described manner and permits the exposed
conduit to be pulled out from the flushing borehole. The old conduit can
hereby be connected with a new conduit in order to be able to execute in
a single operating cycle the withdrawal of the old conduit and the
pulling in of the new conduit. How and when the drill rods are removed
from the flushing borehole is not described.

SUMMARY OF THE INVENTION

[0007] The invention is now based on the problem to technically simplify
the afore-described method and thus to improve it with respect to
construction as well as cost factor.

[0008] This is realized in accordance with the invention by a method of
the afore-stated type in which the old conduit, after being laid bare, is
pulled out and, at the same time but separately, the new conduit is drawn
in.

[0009] It is of particular advantage when the pulling of the old conduit
is concluded by a preferred continuous comminution thereof. A further
substantial economic advantage is realized when the old conduit and the
new conduit are pulled out of the flushing borehole by a common drive.

[0010] This may be implemented by an apparatus having a pulling drive
which is movably arranged on a mounting and acts on the flushing head
rods as well as on the old conduit. The mounting is preferably provided
with a clamping apparatus and/or a guide for the old conduit and the
drive is arranged on a carriage. In order to facilitate comminution of
the old conduit, a clamping apparatus is preferably located behind the
drive.

[0011] In accordance with the conduit replacement according to the
invention, the old conduit, after being washed free, is pulled out of the
flushing borehole in a first operating step with the aid of the drive
acting in the starting pit and, at the same time, the new conduit is
drawn in with the aid of the drill rods. This is implemented in
accordance with the structure of the drill rods in single stages having a
duration which is governed by the length of the rod members in the second
stage of the method.

[0012] The particular advantage of the method according to the invention
is the fact that it has only two stages and accordingly the withdrawal of
the old conduit and the installation of the new conduit is realized at
the same time, preferably with a common pulling apparatus.

BRIEF DESCRIPTION OF THE DRAWING

[0013] An exemplary embodiment of the invention will now be described in
greater detail with reference to the drawing. The drawings show in

[0014]FIG. 1 the simultaneous conduit replacement after the old conduit
has been washed free, and

[0015] FIG. 2 an apparatus for simultaneous pulling in of the new conduit
and pulling out of the old conduit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0016] A channel which has been washed free in a conventional manner
extends between a starting pit 1 and a destination pit 2 and accommodates
an old conduit 4 and a new conduit 5 which is connected by a coupling 6
to a rod assembly 7 comprised of one or more members, whereas the old
conduit 4 is connected directly or via an not shown intermediate piece,
like the rod assembly 7, to a drilling apparatus 8. The drilling
apparatus 8 provides propulsion of a not shown drill head, arranged on
the forward end of the rod assembly 7, for laying the conduit 4 bare as
well as pulling in the new conduit 5 and pulling out the old conduit 4.

[0017] More specifically, the apparatus includes a mounting 9 on which a
drive 10 is movable to incrementally pull out the rod assembly 7 from the
borehole 3 and at the same time to pull in the new conduit 5 via the
coupling 6 as well as to pull out the old conduit 4 from the flushing
borehole.

[0018] This is realized with the aid of the common drive 10 for the rod
assembly comprised of single members, on one hand, and for the old
conduit 4, on the other hand. To render this possible, the rod assembly 7
and the old conduit 4 extend through a clamping apparatus 11 and then to
a rod assembly connection 12 of the common drive 10 and a grab coupling
13 for the old conduit 4. The grab coupling 13 remains closed during
rearward movement of the drive 10 and removal of a rod section and opens
only when the clamping apparatus 11 is closed to then return the drive 10
from its rearward position to its not shown forward position and to
subsequently close again. As a result, one of the clamping apparatuses
11, 13 for the conduit 4 is closed at all times.

[0019] A clamping apparatus 14 for the old conduit 4 is provided in the
rearward part of the mounting 9 and is placed adjacent a shear 15 by
means of which the old conduit 4 is cut into single pieces 16 which can
be easily handled.

[0020] In summary, an apparatus is involved which is simple in structure
and permits a rapid and in particular effective replacement of one or
more old conduits with one or also more new conduits and which, compared
to conventional apparatuses, eliminates an operating step, namely a
separate withdrawal of the exposed old conduit. In addition, the
apparatus enables execution of all essential operating steps with a singe
device.